asp:RegularExpressionValidator error in sharepoint server 2013 wikipage site

hi can anybody help me
to fix this issue

I place a asp.net gridview in a sharepoint 2013 page, I can see the data In the gridview

BUT

When I place a RegularExpressionValidator  to validate a edit textbox , I get this error in the wikipage

Sorry, something went wrong

My asp.net code in the wikipage

<EditItemTemplate>
      <asp:TextBox ID="TextBoxG2" MaxLength="4" runat="server" Text='<%# Bind("Firstname") %>' ValidationGroup="G2">      
      </asp:TextBox>
       <asp:RegularExpressionValidator runat="server" ErrorMessage="RegularExpressionValidator" ValidationGroup="G2" ControlToValidate="TextBoxG2" id="RegularExpressionValidator1"></asp:RegularExpressionValidator>
     </EditItemTemplate>